Systems, apparatus and methods for defining an impairment profile along a polarization quantum channel such as in terms of modal loss and decoherence. The disclosed impairment profile or characterization methods may be used as part of a tool such as to inform a network operator of a weakest span of the communication channel, thus facilitating optimal signal routing decisions.
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1. A method of characterizing an optical channel, comprising: generating, using an entangled photon source (EPS), pairs of entangled photons, wherein first entangled photons A of the generated pairs of entangled photons are coupled to a first optical channel and second entangled photons B of the generated pairs of entangled photons are coupled to a second optical channel, wherein the first channel comprises an optical channel to be characterized and the second channel comprises a local storage optical channel; detecting, at each of the first and second channels, respective entangled photons, wherein each entangled photon A is expressed in the basis (hA, hA′) and each corresponding entangled photon B is expressed in the basis (hB, hB′); determining quantum coincidence data (QCD) of detected entangled photons A and B; measuring quantum-correlation along (hA, hB′) and (hA′, hB) of the detected entangled photons using the determined QCD; and responsive to (hA, hB′) being greater than (hA′, hB), characterizing the first channel as a modal loss first channel; responsive to (hA, hB′) being less than (hA′, hB), characterizing the first channel as a decoherence first channel.
2. The method of claim 1, further comprising: responsive to the first channel comprising a modal loss first channel, configuring the second channel to include a filtering element configured to compensate for modal loss.
3. The method of claim 1, wherein the method is performed at an optical node N within an optical network comprising a plurality of optical nodes, each optical node N transmitting optical information to at least one adjacent optical node N+1 using a respective N first channel.
4. The method of claim 1, wherein the pairs of entangled photons represent photon polarization qubits.
5. The method of claim 1, wherein the pairs of entangled photons represent orbital angular momentum qubits.
6. The method of claim 1, wherein the method is performed at each of a plurality of nodes in an optical network to identify preferred transmission channels thereat.
7. The method of claim 6, wherein a preferred channel at a node comprises modal loss first channel.
8. The method of claim 7, wherein in the absence of a node having associated with it a modal loss first channel, a preferred channel comprises a decoherence first channel having associated with it a lowest amount of decoherence.
9. The method of claim 6, further comprising establishing a connection between a source node SN and a destination node ND within the optical network by entangling photons from the source node, the destination node ND, and any nodes N between the source node SN and destination node ND.
10. The method of claim 9, wherein each node N is configured for receiving an entangled photon AN−1 from a preceding node N−1, performing a Bell State measurement on a locally stored intermediate node photon BN and the received photon AN−1 to entangle thereby a transmitted intermediate node N photon AN and preceding node (N−1) photon BN−1.
11. A method of characterizing an optical channel at an optical node N configured for use within a network comprising a plurality of optical nodes wherein each optical node is coupled to at least one other optical node via respective optical channels, the method comprising: generating, using an entangled photon source (EPS), pairs of entangled photons, wherein first ones A of the generated pairs of entangled photons are coupled to a first optical channel and second ones B of the generated pairs of entangled photons are coupled to a second optical channel, wherein the first channel comprises an optical channel to be characterized; detecting, at each of the first and second channels, respective entangled photons, wherein each photon A is expressed in the basis (hA, hA′) and each corresponding entangled photon B is expressed in the basis (hB, hB′); determining quantum coincidence data (QCD) of detected entangled photons A and B; measuring quantum-correlation along (hA, hB′) and (hA′, hB) of the detected entangled photons using the determined QCD; and responsive to (hA, hB′) being greater than (hA′, hB), characterizing the first channel as a modal loss first channel; responsive to (hA, hB′) being less than (hA′, hB), characterizing the first channel as a decoherence first channel; and selecting a modal loss first optical channel as a transmission channel.
12. The method of an optical node of claim 11, further comprising configuring the second channel to include a filtering element configured to compensate for modal loss.
13. The method of an optical node of claim 11, wherein in the absence of the node having associated with it a modal loss first channel, selecting as a transmission channel a decoherence first channel having associated with it a lowest amount of decoherence.
14. The method of an optical node of claim 11, wherein the optical node is configured to receive an optical communication from an input optical channel and transmit the received optical communication to the selected one of a plurality of output optical channels.
15. The method of an optical node of claim 11, wherein the optical node is configured for receiving an entangled photon AN−1 from a preceding node N−1, performing a Bell State measurement on a locally stored intermediate node photon BN and the received photon AN−1 to entangle thereby a transmitted intermediate node N photon AN and preceding node (N−1) photon BN−1.
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January 24, 2023
April 22, 2025
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